The rotor of an interior permanent magnet motor is such that permanent magnets are embedded in the rotor and the leakage flux from the permanent magnets is reduced by providing air gaps at the permanent magnet end portions. With this configuration, because the leakage flux is reduced as the width of the thin portions, which are present between the rotor outer circumference and the air gaps, in the radial direction becomes smaller, the rotor is often designed such that the width of the thin portions in the radial direction is as small as possible.
When the permanent magnets are present on the surface of the rotor, eddy current generated in the permanent magnets increases and thus the losses increase. Therefore, in some cases, the permanent magnets are embedded on the inner circumferential side of the rotor. In such a case, in order to reduce the width of the thin portions in the radial direction, the air gaps are each formed such that it extends in the rotor outer circumferential direction from the permanent magnet end portion.
In Patent Literature 1, in the rotor of the interior permanent magnet motor, stress concentration caused by the centrifugal force when the rotor is rotating is reduced by bending the air gaps at the permanent magnet end portions in the rotor inner circumferential direction.